In order to analyze a characteristic of a substance, a method for measuring a characteristic of the object to be measured by disposing the object to be measured on a void-disposed structure, irradiating the void-disposed structure on which the object to be measured is disposed with an electromagnetic wave and analyzing a transmission spectrum thereof is employed in general. More specifically, a technique of irradiating an object to be measured such as protein attached to a metal mesh filter with a terahertz wave and analyzing a transmission spectrum can be listed, as an example.
As a prior art of such a technique of analyzing a transmission spectrum with an electromagnetic wave, Patent Document 1 discloses a method constituted of a void-disposed structure (metal mesh, for example) having a void region, an object to be measured being held on a plane of the void-disposed structure, an electromagnetic wave irradiation portion applying an electromagnetic wave toward the object to be measured and an electromagnetic wave detection portion measuring the electromagnetic wave transmitted through the void-disposed structure for measuring a characteristic of the object to be measured on the basis of that the electromagnetic wave projected from the electromagnetic wave irradiation portion toward the void-disposed structure is inclinatorily incident upon the plane including the void region and the position of a dip waveform caused in a frequency characteristic of a measured value moves due to the presence of the object to be measured. As specific methods for holding the object to be measured on the plane of the void-disposed structure, only a method for sticking a support film of polyamide resin or the like to the surface of the void-disposed structure and attaching the object to be measured to the support film and a method for measuring a fluid or a substance dispersed in the fluid by employing an airtight or liquid-tight container in place of the support film are disclosed (Japanese Patent Laying-Open No. 2008-185552: Examples 1 to 3 of Patent Document 1, FIGS. 3, 6 and 10, paragraphs [0017] and [0018]).
In a case of holding the object to be measured on the void-disposed structure through the support film or the like as specifically described in Japanese Patent Laying-Open No. 2008-185552 (Patent Document 1), however, the frequency characteristic of the measured value changes due to the degree of adhesion between the void-disposed structure and the support film or deflection. Further, there has been such a problem that the frequency characteristic is dispersed due to dispersion (thickness dispersion, permittivity dispersion) of the support film itself, to cause dispersion in the measured value.